1. Field Of The Invention
The present invention relates to multi-head printers which have multiple printing modes, and particularly relates to multi-head printers which include a detachable and replaceable paper feed unit which accommodates both wide width printing and standard width printing, wherein the paper feed unit comprises replaceable components such as print roller sections, spur wheels, and friction wheels.
2. Description Of The Related Art
Recently developed printers, such as multi-head ink jet printers are capable of printing across both a standard printing width for print media having standard widths such as 81/2.times.11, legal, A4, etc., and a wide printing width for print media having a width greater than the standard width print media. However, because a majority of the printing performed at the office or at home is limited to standard width print media, the paper feed unit which comprises printer rollers, spur wheels, and friction wheel, wears more heavily along the standard width paper feed path resulting in uneven wear across the paper feed unit.
FIG. 1 illustrates diagrammatically components of a conventional paper feed unit 1. Shown in FIG. 1 are print roller 2, spur wheel 3, friction wheel 4 and drive roller 5, all of which are mounted and rotated along their center axis within the housing of the printer.
Upon performing a print job, recording material P is loaded into the printer and advanced by the printer into paper feed unit 1. Recording material 2 enters between printer roller 2 and spur wheel 3. Recording material P is advanced forward by the clockwise rotation of printer roller 2 and counterclockwise rotation of spur wheel 3. Printer roller 2 is rotated in a clockwise direction by friction roller 4, which is driven by drive roller 5. Spur wheel 3, while having no automatic drive system, is driven in the counter clockwise direction by the friction caused by spur wheel 3 pressing down on recording material P and print roller 2.
Due to the frictional contact between spur wheel 3 and recording material 2, over time the spur edge on spur wheel 3 becomes dull and rounded, and a paper dust is generated. As a result, the rounded spur edge tends to hold ink when feeding a high density printed paper causing a dotted line to be generated on the paper while feeding. Moreover, because the paper dust causes the spur wheel to slip when feeding, the image quality deteriorates and over time continuous paper feeding will contaminate printer roller 2 with paper dust. Typically, only the spur edges on the spur wheels which service the standard width paper feeding path wear, dull and become rounded since standard width recording media is used more frequently and since paper will round and dull the spur edges faster than spur edges contacting its opposing print roller. Therefore, because standard width print media is used more frequently, spur wheels along the standard width paper feed path will wear quicker than spur wheels which service the additional width of the paper feed path.
As explained above, the overall wearing of these components of the paper feed unit is unevenly distributed across the paper feed unit due to a portion of the paper feed unit being used predominantly for feeding standard width print media. This results in improper paper transmissions through the printer which may cause paper jams as well as improper printing quality due to possible buckling of the paper as it is fed through the unevenly worn paper feed unit 1.
Heretofore, it has not been possible to replace worn components or sections of the paper feed unit especially those components which are predominantly used for standard width printing without having to replace unworn components or sections of the paper feed unit or the entire unit itself. Accordingly, it is desirable to detach and replace only certain worn components or sections of the paper feed unit thereby reducing the overall costs of refurbishing the printer.